In addition to Master Proofs, which promote a basic tier class to an upper tier class, there are Change Proofs which allow characters to switch to another basic class (there are limited options set for each character). Units can also use Change Proofs to switch between the corresponding upper tier classes once they've promoted.

I'd imagine they might be pretty rare or secret shop items(else it would just be a preparations mechanic like in FE11 and FE12). Though considering the game has an open map screen with skirmishes I don't think there will be a limit.

Flavia's class seems to have stats about the same as Vake's, so this looks like it confirms her as a Fighter as well. Wait that's Vake; Flavia has a sword. Also, that looks like Sumia in the lower right, but in a different class. The first scan also shows Sumia, and it looks like it has something about Viole. Are there any complete scans?

Hmm. Change Proofs provide a justification for the class change, and they're limited to keep the characters' initial classes relevant. This may be quite okay.

Some other info I've been able to gleam, some confirmed, some not so confirmed.

Not Famitsu, but Nintendo Dream confirms the continent is named Iris, like Krom's homeland.
Feria has two rulers--Basilio of the West and Flavia of the East.
Velvet is the last of the Taguel.
Swordmasters can obtain the Astra skill, which deals 5 consecutive hits with half damage.
Assassins can obtain the Lethality skill, which OHKOs the enemy.
Generals can obtain the Defence Cry skill, which can be triggered on the player and raises the Defence of all adjacent allies.
Pegasus Knights can promote to Dark Pegasus, which can wield magic.

Some other info I've been able to gleam, some confirmed, some not so confirmed.

Not Famitsu, but Nintendo Dream confirms the continent is named Iris, like Krom's homeland.Feria has two rulers--Basilio of the West and Flavia of the East.Velvet is the last of the Taguel.Swordmasters can obtain the Astra skill, which deals 5 consecutive hits with half damage.Assassins can obtain the Lethality skill, which OHKOs the enemy.Generals can obtain the Defence Cry skill, which can be triggered on the player and raises the Defence of all adjacent allies.Pegasus Knights can promote to Dark Pegasus, which can wield magic.